Hundreds of prisoners held by the U.S. military in Afghanistan will for the first time have the right to challenge their indefinite detention and call witnesses in their defense under a new review system being put in place this week, according to administration officials.

The new system will be applied to the more than 600 Afghans held at the Bagram military base, and will mark the first substantive change in the overseas detention policies that President Obama inherited from the Bush administration.

International human rights organizations have long criticized conditions at the Bagram facility, where detainees have been held -- many of them for years -- without access to lawyers or even the right to know the reason for their imprisonment. Afghans have cited Bagram, where virtually all prisoners in U.S. custody are held, as a major source of resentment toward coalition forces, a senior administration official said.

As part of a prison-wide protest that began in July, detainees at Bagram, located north of Kabul, have refused visits from the International Committee of the Red Cross and have declined video teleconferences with their families. The goal of the new procedures, the official said, is to create a "more robust" system that would "allow detainees to tell their story."

Under the new rules, each detainee will be assigned a U.S. military official, not a lawyer, to represent his interests and examine evidence against him. In proceedings before a board composed of military officers, detainees will have the right to call witnesses and present evidence when it is "reasonably available," the official said. The boards will determine whether detainees should be held by the United States, turned over to Afghan authorities or released. For those ordered held longer, the process will be repeated at six-month intervals.

The Bagram system is similar to the annual Administrative Review Boards used for suspected terrorists at the U.S. military prison at Guantanamo Bay, Cuba. Officials said the review proceedings at Bagram will mark an improvement in part because they will be held in detainees' home countries -- where witnesses and evidence are close at hand.

"This process is about doing the right thing -- only holding those we have to," said the administration official, who requested anonymity because he is not authorized to speak publicly about policy.

Human rights organizations briefed by the Pentagon described the new system as a step in the right direction but inadequate. "Any reforms in U.S. detentions in Afghanistan is an improvement, but it remains to be seen whether the new procedures will cure the ills of arbitrary and indefinite detention that have been the hallmark of detentions in Bagram," said Sahr Muhammed Ally of the New York-based group Human Rights First.

Any new procedure, she said, "must provide detainees a legal representative to ensure a meaningful mechanism . . . to challenge their detention, which these procedures do not provide."

Stacy Sullivan, counterterrorism adviser at Human Rights Watch, also said the procedures have to be "meaningful -- not window dressing as we saw at Guantanamo Bay, where the military created a sham review process that looked good on paper but in reality resulted in prolonged detention for men who didn't commit any crimes."

Obama has pledged to close the prison at Guantanamo Bay by the end of the year. An inter-agency panel, led by the Justice Department, is conducting a case-by-case review of some of the 226 remaining detainees there to determine which should be released and which should be subject to legal proceedings. The panel is scheduled to finish its reviews next month and report to the president.

The president has said a small but undetermined number of Guantanamo detainees who are deemed too dangerous to release -- because evidence against them is legally insufficient, cannot be presented in open court or was obtained through what he has called torture -- could be held indefinitely without trial.

An order creating the Detainee Review Boards was signed in July by Deputy Defense Secretary William Lynn and was transmitted to Congress for a required 60-day review period, which ends this week. Pentagon officials have been laying the groundwork to implement the system for the past several weeks, and the first review panels will be held this week.

The Defense Department has said approximately 600 detainees are being held at Bagram, but it has rejected requests by civil and human rights groups to make public the exact number, the detainees' names, or any information about their cases. Although some have been there since the early days of the Afghan war, which began in September 2001, there is considerable turnover with new arrivals and releases. In some cases, U.S. authorities have transferred to Afghan custody those deemed "low-value" insurgents or those arrested for reasons not connected with counterterrorism.

According to human rights organizations, about 500 detainees have been transferred to Afghan authorities since 2007. About 200 have been convicted in Afghan courts, all based on evidence the United States provided. The military is constructing a new prison at Bagram, designed to hold up to 1,000 detainees.

Before 2007, when an "Unlawful Enemy Combatant Review Board" was established at Bagram, there was no formal process to review prisoner status. Until April 2008, detainees were not allowed to attend the reviews. Under the current system, they are given no representation and no opportunity to examine the charges against them or review evidence, and cannot call witnesses.

Most Bagram detainees are Afghans, considered battlefield prisoners taken in a war zone. An unspecified number, said to be fewer than 30, are non-Afghans, many of them captured in other countries. A federal judge ruled this year that three non-Afghan detainees captured elsewhere and held at Bagram were entitled to habeas corpus rights, a decision the administration has appealed.

U.S. courts in general have shown no inclination to interfere with operations in Afghanistan. "Habeas is inappropriate for the battlefield," the administration official said.